One Rep Max Calculator (1RM)

Start Here — One Rep Max Calculator

How to Use One Rep Max Calculator (1RM)

1. Step 1: Choose Units

   Select kilograms (kg) or pounds (lb) to match your plates and bar.

2. Step 2: Enter Weight & Reps

   Type the heaviest weight you lifted for a clean set and the exact number of reps.

3. Step 3: Add RPE (Optional)

   If you track RPE/RIR, select the perceived effort to refine the estimate.

4. Step 4: Review 1RM & Percentages

   Check the blended 1RM and use the working‑set table with rounded targets.

5. Step 5: Load with Plate Math

   Set bar weight and follow the per‑side plate list for fast, consistent loading.

Key Features

• Multiple 1RM formulas (Epley/Brzycki/Lombardi)
• Optional RPE adjustment (RIR‑aware)
• Working‑set % table with rounding
• Plate math per side (kg/lb)
• Mobile‑first UI, large touch targets

Understanding Results

Formulas Used in the One Rep Max Calculator

We estimate your one‑rep max (1RM) from a submaximal set using several widely used rep‑to‑max equations. Showing multiple methods makes the result more robust than any single formula.

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)
• Lombardi: 1RM = weight × reps^0.10
• O’Conner: 1RM = weight × (1 + 0.025 × reps)
• Wathan: 1RM = weight × (100 ÷ (48.8 + 53.8 × e^{−0.075×reps}))

Our display highlights a blended suggestion (median of methods) and rounds to plates in your chosen unit. Respect bar speed and technique—if a set moves slowly or form slips, reduce load.

How to read the numbers

Most programs prescribe work between 65–90% of 1RM. The calculator includes a quick table of common targets with suggested reps (e.g., ~75% for 5×5, ~80% for 3×5, ~85% for 5×3). Use these as starting points and adjust by feel and bar speed.

Assumptions & limitations

Rep quality, range of motion, tempo, fatigue, and technique all influence estimates. Equations are most reliable for controlled sets of 3–8 reps. Treat the result as a planning tool, not a mandate. This site provides educational tools—not medical or coaching advice.

Complete Guide: One Rep Max Calculator (1RM)

Estimate strength fast with our one rep max calculator (1RM). Enter weight and reps to see a blended 1RM, optional RPE, training percentages, and plate math.

The tool turns a normal training set—weight × reps—into a practical one‑rep max (1RM) estimate you can actually use. It blends several common formulas, offers an optional RPE adjustment, and then builds working‑set targets and plate math so you can load quickly. Everything is tuned for a mobile first experience, with large touch targets and clear text you can read while standing by the rack.

What is a one‑rep max (1RM)?

A one‑rep max is the heaviest weight you can lift once with proper form. It’s a useful anchor for programming because many plans prescribe work as a percentage of your 1RM (for example, 75% for sets of 5). In practice, you don’t need to test a true max frequently. A good one rep max calculator lets you estimate 1RM from a clean submax set—safer, faster, and less fatiguing than grinding to an all‑out single.

Use 1RM to compare progress across time and across lifts. For bench press specifically, our bench press calculator builds percent tables and plate math tailored to bench. For lower‑body strength, see the squat max calculator and the deadlift calculator.

Choose a good input set

Your estimate is only as good as the set you enter. Pick a recent, technically solid set done close to failure but not sloppy. For most lifters, 3–8 reps gives stable estimates. Very high reps tend to over‑predict 1RM; very low reps can be sensitive to technique and bar path.

• Record reps that actually counted—no half reps and no bouncing.
• Use the full range of motion you expect to train. Partial ROM inflates estimates.
• Note whether you paused (bench), used straps (deadlift), or used a belt. Keep conditions consistent.
• Log the session RPE or RIR if you track it; the calculator can use it to refine 1RM.

If you’re entering a bench set, consider cross‑checking with the dedicated bench max calculator. Likewise, you can estimate body composition alongside strength trends using the FFMI calculator or plan supporting nutrition with our protein calculator and macro calculator.

Which 1RM formulas do we use?

There’s no single perfect equation for every lifter. Rep‑to‑max formulas model typical performance across rep ranges, but individual technique, fiber type, and training background matter. That’s why our calculator shows multiple estimates and a blended suggestion (the median):

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)
• Lombardi: 1RM = weight × reps^0.10
• O’Conner: 1RM = weight × (1 + 0.025 × reps)
• Wathan: 1RM = weight × (100 ÷ (48.8 + 53.8 × e^{−0.075×reps}))

Showing several methods reduces noise from any single model. If they cluster tightly, your set fits the assumed range well. If one estimate looks like an outlier, trust the middle of the pack and your training experience. Always respect bar speed and form—numbers are a guide, not a command.

RPE/RIR: refine your estimate

RPE (Rate of Perceived Exertion) and RIR (Reps In Reserve) describe how close a set was to failure. A set at RPE 9 implies ~1 rep in reserve; RPE 8, about 2 reps in reserve. If you track RPE/RIR, the calculator can nudge the 1RM estimate by treating the set as if you performed reps + RIR. This is a small but practical adjustment when you keep reps consistent week to week.

Use RPE inputs when you deliberately avoid grinding reps but still want a current training max. If your RPE notes are inconsistent, skip the adjustment and rely on the blended estimate. Consistency beats precision here.

Training percentages that make sense

Most strength work lands between 65–90% of 1RM. Lower percentages emphasize volume and technique; higher percentages build top‑end strength and neural efficiency. You’ll see suggested reps that match each band:

• 90%: 1–2 reps (advanced singles only if bar speed is crisp)
• 85%: 2–3 reps
• 80%: 3–5 reps
• 75%: 5 reps (classic 5×5 zone)
• 70%: 6–8 reps
• 65%: 8–10 reps

For press variations you may handle slightly higher reps at a given percent than you do for the deadlift. Always use the quality of the set as the final judge. If your second rep grinds for three seconds, that weight is too heavy for sets of five on that day.

Rounding, units, and plate math

The calculator rounds to realistic plate jumps: 2.5 kg in metric gyms and 5 lb in imperial gyms. Set your bar weight (20 kg, 15 kg, 45 lb, etc.) and we’ll list plate pairs per side so loading is fast and repeatable. This avoids micro‑loading a number you can’t actually set up during training.

If you want lift‑specific guidance, try these focused tools: bench press calculator, squat max calculator, and deadlift calculator. Each page covers technique notes and set/rep ideas in more detail.

A simple warm‑up ladder

A good warm‑up wakes up the pattern without wasting energy. Here’s a simple ladder based on your estimated 1RM. Keep reps snappy; focus on bar path and bracing.

• Empty bar × 10–15
• ~40% × 5
• ~55% × 3
• ~70% × 2
• ~80% × 1

From there, take your first working set. If bar speed is slower than usual, reduce load 2–5% and keep the day productive. You can track cardiovascular readiness with our max heart rate calculator if conditioning impacts your sets.

How to use 1RM in programs

One 1RM number can power several simple templates. Pick a plan that fits your schedule and recovery. Examples:

• 5×5 @ ~75%: foundational strength and volume. Add small weekly increases.
• 3×5 @ ~80%: slightly heavier with fewer total reps—easier to recover from.
• 5×3 @ ~85%: heavier triples for peaking a lift over a short block.
• Top single @ 85–92.5%, then backoffs (e.g., 3×5 @ 75–80%).

Nutrition supports progress. For targeted protein goals, use the protein calculator, and for energy balance see our calorie calculator and calorie deficit calculator. Matching training to recovery is the fastest path to steady gains.

Technique, safety, and spotting

Use a spotter for heavy benching and safeties for squat and bench if you train alone. Keep the brace, maintain the range of motion you plan to use in testing, and stop sets if form erodes. Estimates don’t give you permission to ignore technique—skill is a performance variable just like strength.

This site provides educational tools, not medical advice. If you’re new to lifting, a few sessions with a qualified coach can shortcut months of trial and error.

When to retest and how to progress

Update your estimate every 3–6 weeks or after a clear PR set (e.g., you added reps at a weight that used to be a grind). You don’t need a formal testing day—just enter your best recent set. If your training cycle calls for peaking, check single @ 90% bar speed and adjust the plan accordingly.

Deloads prevent stalls. Reduce volume or percent for a week when life stress rises or joints feel beat up. Resume with slightly lower loads and rebuild. For body‑composition goals alongside strength, consider the body fat percentage calculator to monitor trends.

Keep notes: exercise variation, bar type, shoes, belt/straps, tempo, rest times. The more consistent your setup, the more consistent your estimates—and the more confidently you can plan your next block.

Common mistakes with 1RM estimates

• Entering a very high‑rep set (e.g., 15+ reps) and treating the result as precise.
• Changing ROM between weeks (e.g., high‑bar vs. low‑bar) and comparing 1RM directly.
• Ignoring bar speed and form warnings because a number says “you should” hit it.
• Rounding to plate loads you can’t set up—plan with the rounding you actually have.

Avoid these and your one rep max calculator estimates will stay realistic and helpful. Numbers are a starting point; the best lifters combine them with smart observation.

Nutrition, recovery, and long‑term progress

Sleep 7–9 hours, eat enough protein, and pace volume. If fat loss is a goal, keep a modest deficit so strength training can still progress—use the macro calculator or maintenance calorie calculator to set targets. Small, consistent steps beat big swings.

Over time, your estimated 1RM graph should trend upward with periodic plateaus. When it stalls, rotate variations (pause work, tempo work), adjust set volume, and rebuild momentum. The goal is sustainable strength—not a single big day followed by a slump.

Frequently Asked Questions